Plasma-jet-gun



Sept. 14, 1955 'r. KUGLER ETAL PLASMA-JET-GUN 2 Sheets-Sheet 1 FiledFeb. 13, 1963 INVENTOR- y/w %9/e/; Ward/Z710 flue/y P 1965 1-. KUGLERETAL 3,206,587

PLASMA-JET-GUN Filed Feb. 13, 1963 2 Sheets-Sheet 2 FIG. 2.

INVENTORS 7/2 0/ 5 02/5 Mad/ImfifiJe/y Wa w United States Patent3,206,587 PLASMA-JET-GUN Tiber Kugler, 2 Zelena, Prague 6,Czechoslovakia, and Vladimir Vesely, 286 Komenskeho, Revnice,Czechoslovakia Filed Feb. 13, 1963, Ser. No. 258,328 8 Claims. (Cl.219-75) The invention relates to a plasma-jet-gun for heat treatment ofvarious materials, more particularly, for depositing coatings fromhigh-melting materials, where the electrodes are specially arranged forresisting erosion by an electric arc and where the chambers housing theelectrodes are sealed against plasma gas leakage. This plasma-jetgun issuitable for application in machine construction works, in metallurgyand chemistry, especially for coatings resistant to heat, abrasion andcorrosion influences.

For these purposes, up to now, use has been made of plasma-jet-gunsworking with inert gases and having a tungsten interior electrode and anexterior electrode provided 'by the outlet nozzle. Besides, applicationhas been made of plasma-jet-guns having a vortex surrounding theelectric arcs trunk, and having a carbon interior electrode.

These appliances are disadvantageous because the plasma-jet-gunsutilizing inert gases for the plasma generating possess a low thermalefficiency, exceeding seldom 50%, and require considerable operatingexpenses. The use of an outlet nozzle as the exterior electrode does notallow to use more than ten percent of hydrogen. It is well known thatthe thermal efficiency of the heated material increases with theincrease of hydrogen content within the plasma. In case of liquidplasma-jet-guns including a carbon electrode, automatic regulation mustbe provided for shifting ahead the carbon electrode which gets consumedat a relative quick rate and must be replaced very often. The wholeconstruction is, therefore, much more complicated in design.

Accordingly, an object of the present invention is to overcome theforegoing difliculties and disadavantages by providing cooled, metallic,rotating electrodes, the consumption whereof is substantially lower thanthat of the carbon electrodes. The advantage well known in regard ofliquid plasma-jet-guns, namely the high energetic eificiency and thepresence of a considerable amount of hydrogen in the plasma, arecombined in this way with those advantages known in respect of gaspla-sma-jet-guns, namely, the low wear of the electrodes and the lack ofprovision of means for automatic shifting of the electrode.

In accordance with the present invention, the plasmajet-gun includes theinterior electrode in form of a cooled metallic ring rotating about anaxis parallel to the channel surrounding the burning electric are. Thisring is mounted upon a carrier and on the periphery whereof a series ofblades is arranged and forms a revolving liquid seal from the liquidhaving entered the space surrounding the electrode which they set inmovement. This seal stands in way to leakage of the plasma gas from theelectrodes chamber and holds the liquid therein at such a level that itdoes neither fill up the electrodes chamber, nor extinguish the electricarc. The liquid may be recirculated into the vortex surrounding theelectric arc. Depending on the material of the electrode, an additivegas is conducted into the chamber surrounding the interior electrodethrough a special channel and orifice. In cases where the materialutilized either is nonconductive, or cannot be attached to the source ofthe electric current, the invention proposes the use of an exteriorrotating electrode situated at the outlet of the plasma from the gun.The electrodes thus have a Substantially larger area than the area ofthe foot of the electric arc, and this foot is then in touch with anyplace of the surface of the electrodes during a short period only.Consequently, the wear of the electrodes is reduced even where hydrogenis present in the plasma gas in a relatively larger proportion. Theincreased dimensions of the electrodes, as compared with the diameter ofthe plasma stream, make possible to place upon the electrodes a greaterfluid amount of material and to yet prolong their lifetime. Thisarrangement makes also superfluous any care for automatic shifting ofthe electrodes towards the electric arc. The dimensions of theelectrodes can be chosen so that there can exist, side by side, severaltrunks of electric arcs, each of which burns Within a separate channel.

Embodiments of the invention have been chosen for purposes ofillustration and description, and are shown in the accompanying drawing,forming a part of the specification, wherein:

FIG. 1 is a sectional view of a plasma-jet-gun provided with rotatinginterior and exterior electrodes with the exterior electrode in form ofa disc placed so that the foot of the electric arc touches the outercircumference of the disc. Both electrodes are made of metal.

FIG. 2 is a sectional view of another embodiment according to theinvention, including the same interior electrode as shown in FIG. 1, buthaving the exterior electrode constructed and arranged so that the footof the electric arc touches its inner circumference.

In the embodiment according to FIG. 1, the stabilization of the trunk ofthe electric arc is achieved within the channel with screens 3, 4 and 6,mounted within a block 7 made of an insulating material. The cylindricalzone of the screen 4 includes tangential orifices 20 and 22 wherethrougha channel 21 feeds-in the working liquid. In the alternative, thecylindric zone of the screen 4 adjacent the screen 6 can include atangential orifice 5 feeding-in the working liquid from the chamber of ainterior electrode 10. This is accomplished by a metallic ring attachedin electrially conductive manner upon a rotating carrier 12 which bearsblades 8 extending forwardly from a flange 9. The carrier 12 contains aconduct for the cooling liquid and a cylindrical zone serving forfurnishing the current from a brush 15. A shaft 14 of the carrier 12lies in a bearing 13 of the block 7. This block 7 contains a channel 18serving to lead gas into the chamber surrounding the interior electrode10. The chamber surrounding the interior electrode 10 is provided withan outlet 16 serving for the liquids outflow. An exterior metallicrotating electrode 23 situated in a bearing 19 in the block and providedwith a current conductor 17 is mounted upon the carrier 12 over aninsulating insert 11. A chamber 24 closed by a packing 25 serves forleading the cooling liquid into the hollow electrode 23. In front of theoutlet screen 3, a baffle or diffuser 1 is placed which is provided withthe orifice 2 for the liquids outflow.

In the embodiment illustrated in FIG. 2, an exterior electrode 32 formedby a metallic ring bearing blades is connected across a metalliccylinder 34 and an insulating insert 35 within a carrier 40 of aninterior electrode 41. In construction, the design of the interiorelectrode 40 is generally identical with that of the embodiment shown inFIG. 1. The electric current is fed to the exterior electrode 32 by abrush 50, and to the interior electrode by a brush 46. The system ofelectrodes is housed by an insulating block 31. The stabilizationchannel is formed by screens 36, 37, and 38, and is placed within aninsulating block 55. The screens 36 and 38 are provided with outlets 57and 56 through which the liquid flowing from the channel is lead away.The block 55 is placed concentrically with the system of electrodes sothat there remains between it and the insulating insert 35 a sufficientgap allowing the liquid to flow through. In the block 55, a channel 54with a branch 48 serves for leading the liquid into the stabilizing zoneand includes a branch 47 leading the liquid into the carrier 40 of anelectrode 41 through an orifice 43. Channels 53 and 49 serve forconducting gas into the chamber surrounding the interior electrode 41.The channels 51 and 52 lead the liquid out of the gap between theinsulating cylinder 35 and the block 55.

The apparatus according to the invention shown in FIG. 1 works so that,in the region between the interior electrode 10 and the exteriorrotating electrode 23, the electric arc burns within the channel formedby the liquid vortex. Through a conduit 18 along the electrode 10, a gascan be fed in addition. The quantity and kind of this gas are fixed bytechnologic requirements and by the art of the metal whereof theelectrode 10 is manufactured. It is well known that the erosive actionof the electric arc causes abrupt wear upon electrodes made of certainkinds of metallic materials, and that this wear can be substantiallyreduced when hydrogen is not allowed to come in any greaterconcentration in immediate proximity of the electrodes. Where use wasmade of certain metallic materials, it is, besides, highly advantageousto form a tin oxide layer upon their surface. Hereto, it will suflice agas, e.g. the air, in such a small quantity only which does notinfluence in excess the concentration of hydrogen in the outfiowingplasma stream. The presence of a non-condensing gas retards, besides,the condensation of plasma vapours within the electrodes chamber, sothat the energy of the plasma is prevented from being conducted into theliquid in the chamber of the interior electrode 10. From the channel, apart of the liquid flows over the surface of the screen 6 into theelectrodes chamber where the blades 8 induce it into rotating movement.In this way, this liquid and that one which flows through the channelsin the carrier 12, form, in the periphery of the chamber, a liquid ringwhich stops any leakage of the gas from the electrode chamber. Theliquid of this ring is lead away through the orifice 16. Where therevolution of the electrodes has been chosen so that centrifugal forcesgive the liquid ring a sufiiciently high pressure, the outflow, insteadof ensuing through the orifice 16, may be carried out through thechannel which conducts thereafter the liquid into the vortex movementWithin the channel area. In coming into the vortex in this case, theliquid is already preheated so that heat losses are loweredconsiderably. The possibility to exploit sufficiently rapid revolutionof the electrodes depends on physical and mechanical properties of theconstruction material of the carrier 12, and on electric properties ofthe materials of the electrodes 10 and 23 which must allow sutficientlyquick movement of the respective electrode under the foot of theelectric arc, without adversely affecting its stability. The liquid forcooling the exterior electrode 23, and the interior electrode 10, is fedthrough the chamber 24 sealed-up by packing 25, across the hollowelectrode 23 and through its hollow shaft towards the electrode 10. Theliquid flowing out of the channel over the surface of the screen 3 islead away by bafiling action of the ditfusor 1 towards the outletorifice 2.

In the embodiment illustrated in FIG. 2, the blades 39 on the carrier 40of the interior electrode 41, and the blades 33 of the exteriorelectrode 32 create a rotating annular stopper barring the gas inleaking from the chamber surrounding the electrode 41, through the gapexisting between the insulating cylinder 35 and the block 55. From thering, the liquid is carried away by the channels 51 and 52. The electricarc burns between the interior circumference of the electrode 32 and theannular interior electrode 41. The liquid is brought into the vortexmovement through the conducts 54 and 48, and over the surfaces of thescreens 36 and 38, and, having been directed by the projections 57 and56, flows down into the liquid ring.

In both the embodiments, the plasma is generated from the liquid formingthe walls of the vortex channel. Its composition might be broadlychanged with regard to the technology to be followed, either in choiceof the proper liquid, or in kind and quantity of the additional gas fedinto the chamber surrounding the interior electrode 41.

The disc of the interior electrode 23, as shown in FIG. 1, may be set inrotating movement not only by mechanical coupling with the carrier 12 ofthe interior electrode, but also by help of its proper drive, or by adrive transmission between the exterior electrode and the carrier of theinterior electrode 12. The liquid for refrigeration of the electrodescan be introduced through separate inlets. The choice of the electrodespolarity depends on their material and on the composition of the liquidand the additive gas applied.

The invention will find application in cases of surface heat-treatmentsof metallic constructions and installations carried out by deposition ofceramic, metallo-ceramic or metallic coatings having to resist to highheats amounting to 1500 C. and more, i.e. particularly in combustionturbines, and thermal energy installations in general. In course of thedeposition, the gun according to the invention forms sufficiently hightemperatures up to 25,000 C. The coating the gun is able to deposit, isthen highly resistant to abrasion and to chemically aggressive media,because of being formed by oxide materials (A1 0 ZrO and the like), bycarbide materials (carbides of tungsten, titanium, tantalum, boron,nitrides, borides etc., and their mixtures with metals, the s.c.cermets).

It is quite natural that the application of the gun according to theinventions is by far not limited to this manner of exploitation. It canbe advantageously utilized for heating of materials, as eg for cuttingof metals, for melting dissociation of minerals, i.e. wherever thematerial shall be affected by an intense thermal source having a hightemperature gradient in the melting focus.

What is claimed is:

1. In a plasma-jet-gun, the combination of a housing having a channelfor stabilizing the trunk of an electric arc and having passageway meansfor introducing plasma generating gas into said channel, an interiormetallic electrode facing the inner end of said channel and an exteriorelectrode adjacent the outer end of said channel for establishing theelectric arc in said channel, means for mounting said electrodes forrotation about an axis parallel to the axis of said channel, and drivemeans for rotating said electrodes, said housing and said electrodeshaving passageway means for circulating a liquid for cooling saidhousing and said electrodes.

2. In a plasma-jet-gun according to claim 1, wherein said electrodes arecircular, said interior eletrode has a disc portion facing the inner endof said channel, and said exterior electrode has a cylindrical portionfacing the axis of said channel and adjacently spaced therefrom.

3. In a plasma-jet-gun according to claim 2, wherein said cylindricalportion faces radially outwardly.

4. In a plasma-jet-gun according to claim 2, wherein said cylindricalportion faces radially inwardly.

5. In a plasma-jet-gun according to claim 1, wherein at least one ofsaid electrodes has blades on the periphery thereof and said housing haspassageway means for directing a portion of the liquid against saidblades to provide said means for rotating said electrodes.

6. In a plasma-jet-gun according to claim 5, wherein both of saidelectrodes are provided with said blades.

7. In a plasma-jet-gun according to claim 1, wherein said housing haspassageway means for establishing a shield of cooling liquid about thetrunk of the electric are passing through said channel.

8. In a plasma-jet-gun according to claim 1, wherein said electrodeseach have a commutating ring and a brush engages each of said rings forconducting electrical current to said electrodes.

References Cited by the Examiner UNITED STATES PATENTS 3,047,709 7/62Browning 219-75 5 3,082,314 3/63 Arata et al. 219-75 3,097,292 7/ 63Kugler et al. 219121 3,116,405 12/63 Browning et al. 219-75 RICHARD M.WOOD, Primary Examiner.

10 JOSEPH V. TRUHE, SR., Examiner.

1. IN A PLASMA-JET GUN, THE COMBINATION OF A HOUSING HAVING A CHANNELFOR STABILIZING THE TRUNK OF AN ELECTRIC ARC AND HAVING PASSAGEWAY MEANSFOR INTRODUCING PLASMA GENERATING GAS INTO SAID CHANNEL, AN INTERIORMETALLIC ELECTRODE FACING THE INNER END OF SAID CHANNEL AND AN EXTERIORELECTRODE ADJACENT THE OUTER END OF SAID CHANNEL FOR ESTABLISHING THEELECTRIC ARC IN SAID CHANNEL, MEANS FOR MOUNTING SAID ELECTRODES FORROTATION ABOUT AN AXIA PARALLEL TO THE AXIS OF SAID CHANNEL, AND DRIVEMEANS FOR ROTATING SAID ELECTRODES, SAID HOUSING AND SAID ELECTRODESHAVING PASSAGEWAY MEANS FOR CIRCULATING A LIQUID FOR COOLING SAIDHOUSING AND SAID ELECTRODES.